The Difference Between Delay and Disruption
One moves the completion date. The other erodes productivity without ever touching it. Most claims fail because the two get argued as if they were the same thing, with the same evidence. |
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WHAT HAPPENED · ILLUSTRATIVE COMPOSITE
A contractor finishes on the certified completion date. There was no need for an extension – the critical path was never really under threat. But three trades spent four months working out of sequence around a design change, re-mobilising twice and carrying out labour at half the planned output.
The final account includes a loss and expense claim for that inefficiency. The employer's quantity surveyor rejects it on a single line: there was no delay, so there is no basis for a claim. The contractor is confused, because nobody disputes that the design change happened or that it cost real money.
Both positions rest on the same error: treating delay and disruption as the same claim. They are not. The contractor never needed to prove delay. It needed to prove that regular progress was materially affected — a different question, with a different evidential answer.
Why the distinction gets lost
Two different measurements. Delay is measured against the programme's critical path and the completion date. Disruption is measured against planned productivity — the labour, plant and sequencing assumed at tender against what actually happened on site. An event can cause one without the other. A design change absorbed entirely within float causes disruption with no delay at all. A strike on a non-critical subcontract package can delay that package without touching the programme's critical path or disrupting anyone else's output.
Scope and sources. This article addresses the FIDIC Conditions of Contract for Construction 2017 (2nd edition) and JCT Standard Building Contract with Quantities 2016, together with the leading English authority on concurrent delay. The JCT 2024 suite and NEC4 are not covered. The case above is a constructed composite; the clause mechanics and the case law are real.
“A project can finish exactly on time and still be a financial disaster for the contractor. Delay and disruption are measured against different things, and proving one proves nothing about the other.”
FIDIC — one clause covers both, badly if you let it
The delay side. Sub-Clause 8.5 lists what entitles the Contractor to an Extension of Time: a Variation; a cause of delay arising under another Sub-Clause; exceptionally adverse climatic conditions; Unforeseeable shortages of personnel or Goods caused by epidemic or governmental action; and any delay, impediment or prevention caused by or attributable to the Employer, the Employer's Personnel, or the Employer's other contractors on the Site.
Which is why disruption claims under FIDIC are harder. FIDIC has no separate defined concept of disruption. Where the Conditions use the word at all, it is folded into Sub-Clause 8.5 itself — delay caused by public authorities is treated as a cause of delay under the same sub-clause whether the effect was to delay completion or merely to disrupt the Contractor's work. Financial recovery for either follows the ordinary route through Sub-Clause 20.2, provided the underlying cause is one that carries a Cost entitlement and not simply time.
So the real question is always: which sub-clause, and does it pay Cost. That distinction matters commercially. Not every Sub-Clause 8.5 event carries Cost. Exceptionally adverse climatic conditions give time only. Employer-caused prevention under sub-paragraph (e) generally carries both. A contractor arguing productivity loss under FIDIC has to identify which specific event caused it and check whether that event's own sub-clause gives a right to Cost — disruption is not a free-standing head of claim.
Concurrency is expressly addressed — but only if you draft it. The 2017 edition also does something the 1999 form did not: it addresses concurrency directly. Where a delay caused by a matter that is the Employer's responsibility runs concurrently with a delay caused by a matter that is the Contractor's responsibility, entitlement to EOT is assessed according to rules stated in the Special Provisions or, failing that, as appropriate to the circumstances. FIDIC leaves the mechanism to be drafted — which means a contract with blank Special Provisions has no agreed concurrency rule at all, and the parties are arguing method as well as fact when the dispute arrives.
JCT — two lists, two tests, two burdens of proof
The delay list. JCT keeps delay and disruption structurally separate, which is clearer in theory and just as commonly conflated in practice. Clause 2.29 lists the Relevant Events that entitle the Contractor to a fair and reasonable extension of time. That list governs the completion date and nothing else.
The disruption test. Loss and expense runs on a different test entirely. Clause 4.20 entitles the Contractor to reimbursement where regular progress of the Works, or any part of them, has been or is likely to be materially affected by a Relevant Matter — deferment of possession, or one of the other listed matters. The trigger is not delay to the Completion Date. It is a material effect on regular progress, which a contractor can suffer while still finishing on programme, exactly as in the composite above.
Two claims, two proofs. Clause 4.21 then sets the evidential burden: the Contractor must notify as soon as the likely effect on regular progress becomes, or should reasonably have become, apparent, and the ascertainment that follows is a factual exercise, not an automatic consequence of an EOT being granted. Winning an extension of time proves nothing about loss and expense, and losing one does not defeat it — they are decided on their own facts against their own tests.
What the courts said about concurrency
The English approach. Concurrent delay is the point where the delay/disruption distinction collides with causation doctrine, and English law took a clear position in Walter Lilly & Company Ltd v Mackay and another [2012] EWHC 1773 (TCC). Akenhead J, sitting in the Technology and Construction Court, confirmed what has become known as the Malmaison approach, after the earlier decision in Henry Boot Construction (UK) Ltd v Malmaison Hotel (Manchester) Ltd (1999) 70 Con LR 32: where delay results from two or more effective causes, and at least one of them is a Relevant Event for which the employer bears the risk, the contractor is entitled to a full extension of time — not a reduced or apportioned one.
Why he decided it that way. Akenhead J's reasoning rested on two grounds. Many of the events giving an entitlement to extension of time are themselves acts of prevention by the employer, and a party should not lose the benefit of an extension because its own default happened to coincide with the employer's. And, reading the JCT extension of time clause as a matter of construction, nothing in its wording supported reducing the contractor's entitlement merely because a concurrent cause also existed.
It is not a settled international rule. That is not the only common law answer. The Scottish courts, in City Inn Ltd v Shepherd Construction Ltd, took the opposite view and apportioned time between the competing causes rather than awarding it in full. English and Scots law diverge on this point, and a Nigerian contract governed by a form silent on concurrency inherits that uncertainty rather than resolving it — which is precisely why FIDIC 2017 now asks the parties to draft their own rule instead of leaving it to whichever jurisdiction's default a court happens to apply.
And the standard for proving disruption. Walter Lilly also fixed the standard for proving disruption itself, at paragraph 486 of the judgment. A contractor advancing a delay and disruption loss and expense claim must show, on the balance of probabilities, that qualifying events occurred, that those events caused delay or disruption, and that the delay or disruption caused it to incur loss and expense. The court accepted that a contractor need not achieve scientific precision in pleading cause and effect — the three-limb chain can be proved by whatever evidence satisfies the tribunal on the ordinary civil standard.
Two qualifications. Two qualifications for a Nigerian reader. Walter Lilly is an English Technology and Construction Court decision, persuasive rather than binding here, and it construes the JCT form specifically rather than FIDIC. The three-limb causation test is nonetheless the clearest available statement of what a disruption claim actually has to prove, on any form.
“A project can finish exactly on the certified date and still be a financial disaster for the contractor. Proving delay proves nothing about disruption, and proving disruption proves nothing about delay.”
The case for keeping them merged
The obvious objection. Everything above argues for separating the two claims sharply. There is a respectable argument for not overcomplicating a small dispute by insisting on that separation, and it deserves stating.
The argument. On a modest project, running two fully separate evidential exercises — a critical path analysis for delay and a measured-mile productivity study for disruption — can cost more in professional fees than the sums genuinely in dispute. Where an event plainly caused both problems together, as a major redesign often does, a combined narrative supported by contemporaneous records may be proportionate even if it is not the analytically purest way to present the claim.
Where the line actually sits. The risk is not proportionality itself; it is proportionality mistaken for rigour. Walter Lilly's three-limb test still has to be satisfied for the disruption element even inside a combined claim, and a certifier or tribunal that cannot see which evidence supports which limb will discount the whole claim rather than untangle it. Combining the narrative is a proportionate choice about presentation. Combining the proof — asserting that delay evidence establishes disruption, or the reverse — is the error the composite at the start of this article illustrates.
What to build into the records before either claim is needed
First. Keep programme records and productivity records as two distinct sets from day one. A critical path network proves delay. Daily allocation sheets, planned-versus-actual output records, and a genuinely undisturbed comparison period prove disruption. Neither substitutes for the other.
Second. On FIDIC, check what the Special Provisions say about concurrency before a dispute arrives, not during one. A blank entry means the point is unresolved and will be argued as a matter of general law rather than contract.
Third. On JCT, serve the clause 4.21 notice on the disruption effect separately from any clause 2.29 extension of time application, even where both arise from the same event. They are different notices answering different questions, and a single combined letter risks satisfying neither test properly.
Fourth. Build the three-limb chain from Walter Lilly into every loss and expense file as it is opened: which event, what effect on progress, what loss resulted. A claim assembled against that structure from the outset survives scrutiny; one reconstructed after the event rarely does.
Finishing on time and losing money are not contradictory facts.
Delay is measured against the completion date. Disruption is measured against planned productivity. A project can fail one test and pass the other, and proving one proves nothing about the other. FIDIC folds disruption into the same clause as delay and pays for it only where the underlying event carries Cost. JCT keeps them on separate lists with separate tests. Walter Lilly sets the standard both still have to meet: event, effect, and loss, each proved in turn. Build records that prove each limb from the day the event happens, not the month the final account is due.
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CLAUSE REFERENCES
FIDIC Conditions of Contract for Construction 2017 (2nd ed): Sub-Clause 8.5 [Extension of Time for Completion], including the concurrency provision in its final paragraph; Sub-Clause 20.2 [Claims For Payment and/or EOT]; Sub-Clause 2.5 [Site Data and Items of Reference].· JCT Standard Building Contract with Quantities 2016: cl. 2.29 (Relevant Events); cl. 4.20 (Loss and Expense — matters materially affecting regular progress); cl. 4.21 (notification and ascertainment). The JCT 2024 suite is not covered.· Walter Lilly & Company Ltd v Mackay and another [2012] EWHC 1773 (TCC), Akenhead J — an English Technology and Construction Court decision, persuasive rather than binding in Nigeria, applying the Malmaison approach from Henry Boot Construction (UK) Ltd v Malmaison Hotel (Manchester) Ltd (1999) 70 Con LR 32, and setting the three-limb causation test for delay and disruption loss and expense claims at ¶486. Contrast City Inn Ltd v Shepherd Construction Ltd (Scotland), which favours apportionment on concurrency. Permission to appeal Walter Lilly was refused: [2013] EWCA Civ 142.· NEC4 is not covered.
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